I use two heat sources for my crabitat. I use a good quality under tank heater... and a heat lamp.

Do your research on under tank heaters... none are inexpensive and none are made for what we are using them for. They are made to go under the tank and we DONT want them under the tank... Because if we put them under the tank it will dry out the substrate and heat it up... great for reptiles and very bad for hermits...

Hermits need the substrate to be moist and the temp to be the same as the enclosure...more or less.. around 80 F - So you have to go up in size on the UTH and place it on the back glass just above or right at the substrate line... this helps heat the enclosure... I leave mine on year round to create an area of higher heat in the back of the tank... my tank is a 40g breeder tank. I tried a couple different cheaper brands (zoomed, etc..) that ended up in the trash, I ended up using an outdoor heated mat (has controller) that is used to melt snow. Even a heating pad for people on low might be good because you don't have to stick it to the tank, and it is washable. There are many people on the reptile forums that recommend this. And then there are good quality UTHs out there and someone has already given you a link to one that may be a good one. I just want to let you know that the common ones in the local box stores are not them. So don't waste your money and your time... scraping them off the glass is a pain! :whistling:

As for the heat lamp... You can use a plain incandescent bulb though they are getting harder to find as the laws that govern them have changed in the US. IF you use a white bulb it is best that it go off at night... Since it is coldest at night, you may want to go with a red bulb so you can leave it on. The red bulbs don't bother the Hermits. Either way be sure that you do not get a bulb that says it is a 'basking, or spot' heat lamp for reptiles that puts the heat in a concentrated area... but one that heats the entire enclosure... A spot lamp will cook the Hermits. In the winter I put extra insulation around my Hermit tank in the form of blankets or whatever I have that I think will work. I keep my lights on a timer and my red lights come on in the evening and I have at least two sources of heat so that if one goes out, for example a bulb, I have a backup.